Many document copying machines require that a document be held in a stationary manner face down on a document glass in order to be copied. Frequently, in a copier of this type, it is necessary for the operator to place the document on the document glass manually. However, in some machines, the operator may feed documents onto the document glass by inserting them one at a time into an automatic feeding arrangement. Mechanisms of this type are known as semiautomatic document feeds (SADF). In other machines, the operator may place a stack of documents upon a feed tray from which they are automatically fed. Mechanisms of this second type are known as automatic document feeds (ADF). Other document copying machines require that the document move across a narrow slit type viewing station whereat the moving document is scanned by stationary optics.
Whether a stationary or moving document copier is used, and whether a semiautomatic document feed or an automatic document feed is utilized, it is necessary for the feeder to provide mechanisms which move the paper across the document glass. A particularly useful type of forwarding mechanism is a system of rollers which in the case of a stationary document copier bear against the document glass as shown in U.S. Pat. No. 4,285,512, incorporated herein by reference. In this patent, the forwarding rollers may be made of a foraminous material positioned above the document glass at a slight angle, about 3.degree., to the direction of document movement in order to move the side of the document into a sliding relationship with a reference edge during the forwarding operation. The angle is produced by a curved drive shaft.
While the document feed of the above-mentioned patent is a reliable and convenient mechanism for copying original documents, it copies one side of the original document only before exiting that document to an exit pocket. Consequently, if it is desired to copy both sides of a duplexed original, it is necessary for the operator to remove the document from the exit pocket, place it on the ADF tray or enter it into the SADF, in either case with the opposite side down. In performing this operation, there is some potential for operator error since the wrong side might be copied or the operator might turn the copy so that it is copied end for end. In addition, it requires a manual operation which can be inconvenient. After the copy is made and the original exits the document glass, the operator then has the added inconvenience of manually turning the original over in order to preserve correct order in a set of duplexed originals. It is the general object of this invention to improve the document feed device described in the above-named patent by providing mechanisms which automatically copy a duplexed original document before exiting the document.